Creating posts is nothing special if you have even basic experience with WordPress. Holomatic theme offers couple of additional options in Post editor.
Holomatic supports couple format of posts - image and video. You can change it in right sidebar in post edit screen. Default is Standard - that one shows only text of post and thumbnail image if added. Each change of post format will show a form with options to fill.
Embed video from services like Youtube, Vimeo, or Hulu. You can find a list of supported oEmbed sites in the Wordpress Codex. Alternatively, you could use the built-in
Embed audio from services like SoundCloud and Rdio. You can find a list of supported oEmbed sites in the Wordpress Codex. Alternatively, you could use the built-in
After switching post type to Gallery, you'll see a box with blue "Create Gallery", click it to select photos you want to show in Gallery. There are two types of gallery, you can choose one in option below the button. First one is standard slider based on RoyalSlider script
next one, named PhotoGrid - fits the photos from gallery into nice looking max 4 columns grid
Except the standard WordPress settings for posts, there's also Layouts option box
You can select post layout - left sidebar, right sidebar, or full-width post, and assign which Sidebar to display on this post view. You can create custom sidebars in Appearance -> Theme Options